■ FEWER POLLUTANTS—Vehicles caught in stop-and-go traffic emit far more
pollutants, particularly carbon monoxide, nitrogen oxides, and smog-
forming volatile organic compounds, than they do without frequent
braking and acceleration.
■ REDUCTION IN GREENHOUSE GASES—Improving traffic flow and reducing
congestion will decrease atmospheric carbon dioxide.
■ IMPROVED FUEL ECONOMY—For vehicles stuck in traffic, not only do
tailpipe emissions go up, but fuel economy goes down. Modest
improvements to the nation’s worst traffic bottlenecks would save $1
billion in gallons of fuel each year and would help reduce the dependency
on foreign oil.
■ IMPROVED ECONOMY—Interstates return $6 in economic productivity for
every $1 invested.
■ IMPROVED QUALITY OF LIFE—An interstate highway system allows
products (both perishable and nonperishable) to be distributed throughout
the country in a short period of time.Canals and Channels
The two largest canals of major economic value in the world are the Panama
Canal, which connects the Pacific Ocean with the Atlantic and allows water
transport without having to travel around South America, and the Suez Canal,
which connects the Red Sea with the Mediterranean and allows water transport
between Europe and Asia without traveling around Africa.
Completed in 2016, the Panama Canal expansion project, also called the
Third Set of Locks Project, doubled the capacity of the current Panama Canal by
adding a new lane of traffic. This allowed for a larger number of ships and
increased the width and depth of the lanes and locks. The new, larger size of
ships that are now able to pass through the canal are about one and a half times
the previous ship size and can carry over twice as much cargo.
Although it is too early to assess the actual environmental impacts of the
Third Set of Locks Project, examples of environmental concerns include:
■ Harm (e.g., biodiversity) to surrounding forests, national parks, and forest
reserves and the wildlife living therein
■ Impact on agricultural areas
■ Impact on freshwater supplies (e.g., Lake Gatún) and water quality (e.g.,
salinization)